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piston (top) and connecting rod from typical automotive engine (scale is in centimetres)

Components of a typical, four stroke cycle, DOHC piston engine. (E) Exhaust camshaft, (I) Intake camshaft, (S) Spark plug, (V) Valves, (P) Piston, (R) Connecting rod, (C) Crankshaft, (W) Water jacket for coolant flow.

In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Image File history File links Question_book-3. ... piston + connecting rod © scan, upload by MH 22:11, 2004 Aug 23 (UTC) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... piston + connecting rod © scan, upload by MH 22:11, 2004 Aug 23 (UTC) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... Labeled diagram of a four-stroke engine, created by Wapcaplet in Blender. ... Labeled diagram of a four-stroke engine, created by Wapcaplet in Blender. ... The four-stroke cycle of an internal combustion engine is the cycle most commonly used for automotive and industrial purposes today (cars and trucks, generators, etc). ... For the fictional characters of the same name, see Camshaft (Transformers). ... This article or section should include material from Spark gap A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark. ... A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. ... For the American composer, see Walter Piston. ... Crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black) Continental engine marine crankshafts, 1942 Components of a typical, four stroke cycle, DOHC piston engine. ... Components of a typical, four stroke cycle, DOHC piston engine. ... For the American composer, see Walter Piston. ... Crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black) Continental engine marine crankshafts, 1942 Components of a typical, four stroke cycle, DOHC piston engine. ...

Internal combustion engines

Failure of a connecting rod is one of the most common causes of catastrophic engine failure.

In modern automotive internal combustion engines, the connecting rods are most usually made of steel for production engines, but can be made of aluminium (for lightness and the ability to absorb high impact at the expense of durability) or titanium (for a combination of strength and lightness at the expense of affordability) for high performance engines, or of cast iron for applications such as motor scooters. They are not rigidly fixed at either end, so that the angle between the connecting rod and the piston can change as the rod moves up and down and rotates around the crankshaft. Image File history File linksMetadata Download high-resolution version (1412x1030, 297 KB)Picture of a broken piston and connecting rod from a scooter. ... Image File history File linksMetadata Download high-resolution version (1412x1030, 297 KB)Picture of a broken piston and connecting rod from a scooter. ... Car redirects here. ... A colorized automobile engine The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. ... For other uses, see Steel (disambiguation). ... Aluminum redirects here. ... General Name, symbol, number titanium, Ti, 22 Chemical series transition metals Group, period, block 4, 4, d Appearance silvery grey-white metallic Standard atomic weight 47. ... Cast iron usually refers to grey cast iron, but can mean any of a group of iron-based alloys containing more than 2% carbon (alloys with less carbon are carbon steel by definition). ... Crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black) Continental engine marine crankshafts, 1942 Components of a typical, four stroke cycle, DOHC piston engine. ...

The small end attaches to the piston pin, gudgeon pin (the usual British term) or wrist pin, which is currently most often press fit into the con rod but can swivel in the piston, a "floating wrist pin" design. The big end connects to the bearing journal on the crank throw, running on replaceable bearing shells accessible via the con rod bolts which hold the bearing "cap" onto the big end; typically there is a pinhole bored through the bearing and the big end of the con rod so that pressurized lubricating motor oil squirts out onto the thrust side of the cylinder wall to lubricate the travel of the pistons and piston rings. In internal combustion engines piston engines, the gudgeon pin is that which connects the piston to the connecting rod and provides a bearing for the connecting rod to pivot as it moves. ... An Interference fit (sometimes called a Press fit) is a fastening between two parts which is achieved by friction after the parts are pushed together, rather than by any other means of fastening. ... Crankshaft (red), pistons (gray) in their cylinders (blue), and flywheel (black) Continental engine marine crankshafts, 1942 Components of a typical, four stroke cycle, DOHC piston engine. ... It has been suggested that Bushing be merged into this article or section. ... This article is about screws and bolts. ... A lubricant (colloquially, lube) is a substance (often a liquid) introduced between two moving surfaces to reduce the friction and wear between them. ... A typical container of motor oil, with some in a glass. ... Thrust is a reaction force described quantitatively by Newtons Second and Third Laws. ... Cylinder with piston in a steam engine A cylinder in the central working part of a reciprocating engine, the space in which a piston travels. ... Spring-loaded piston rings. ...

The con rod is under tremendous stress from the reciprocating load represented by the piston, actually stretching and relaxing with every rotation, and the load increases rapidly with increasing engine speed. Failure of a connecting rod, usually called "throwing a rod" is one of the most common causes of catastrophic engine failure in cars, frequently putting the broken rod through the side of the crankcase and thereby rendering the engine irreparable; it can result from fatigue near a physical defect in the rod, lubrication failure in a bearing due to faulty maintenance, or from failure of the rod bolts from a defect, improper tightening, or re-use of already used (stressed) bolts where not recommended. Despite their frequent occurrence on televised competitive automobile events, such failures are quite rare on production cars during normal daily driving. This is because production auto parts have a much larger factor of safety, and often more systematic quality control. A cast 6-cylinder BMW engine block For the G.I. Joe character, see List of G.I. Joe ARAH characters. ... In materials science, fatigue is the progressive, localised, and permanent structural damage that occurs when a material is subjected to cyclic or fluctuating strains at nominal stresses that have maximum values less than (often much less than) the static yield strength of the material. ... Factor of safety (FoS) can mean either the fraction of structural capability over that required, or a multiplier applied to the maximum expected load (force, torque, bending moment or a combination) to which a component or assembly will be subjected. ... For the Jurassic 5 album, see Quality Control (album) In engineering and manufacturing, quality control and quality engineering are involved in developing systems to ensure products or services are designed and produced to meet or exceed customer requirements. ...

When building a high performance engine, great attention is paid to the con rods, eliminating stress risers by such techniques as grinding the edges of the rod to a smooth radius, shot peening to induce compressive surface stresses (to prevent crack initiation), balancing all con rod/piston assemblies to the same weight and Magnafluxing to reveal otherwise invisible small cracks which would cause the rod to fail under stress. In addition, great care is taken to torque the con rod bolts to the exact value specified; often these bolts must be replaced rather than reused. The big end of the rod is fabricated as a unit and cut or cracked in two to establish precision fit around the big end bearing shell. Therefore, the big end "caps" are not interchangeable between con rods, and when rebuilding an engine, care must be taken to ensure that the caps of the different con rods are not mixed up. Both the con rod and its bearing cap are usually embossed with the corresponding position number in the engine block. A stress concentration or stress raiser is a location in an object where stress is concentrated. ... Hearst Mining building (stone, left) with expansion (shot peened aluminum alloy, right). ... Magnafluxing is a method of testing ferrous metals for surface and subsurface flaws. ...

Recent engines such as the Ford 4.6 liter engine and the Chrysler 2.0 liter engine, have connecting rods made using powder metallurgy, which allows more precise control of size and weight with less machining and less excess mass to be machined off for balancing. The cap is then separated from the rod by a fracturing process, which results in an uneven mating surface due to the grain of the powdered metal. This ensures that upon reassembly, the cap will be perfectly positioned with respect to the rod, compared to the minor misalignments which can occur if the mating surfaces are both flat. Powder metallurgy is a forming and fabrication technique consisting of three major processing stages. ...

A major source of engine wear is the sideways force exerted on the piston through the con rod by the crankshaft, which typically wears the cylinder into an oval cross-section rather than circular, making it impossible for piston rings to correctly seal against the cylinder walls. Geometrically, it can be seen that longer con rods will reduce the amount of this sideways force, and therefore lead to longer engine life. However, for a given engine block, the sum of the length of the con rod plus the piston stroke is a fixed number, determined by the fixed distance between the crankshaft axis and the top of the cylinder block where the cylinder head fastens; thus, for a given cylinder block longer stroke, giving greater engine displacement and power, requires a shorter connecting rod (or a piston with smaller compression height), resulting in accelerated cylinder wear. Cylinder with piston in a steam engine A cylinder in the central working part of a reciprocating engine, the space in which a piston travels. ... This oval, with only one axis of symmetry, resembles a chicken egg. ... Spring-loaded piston rings. ... Stroke can mean: In medicine, a cerebrovascular accident (or cerebral accident) A sunstroke In writing, a single line without any break such as stroke in graphics or Chinese characters, see stroke order. ... The cylinder head from a GMC van. ... One complete cycle of a four cylinder, four stroke engine. ...

In certain types of engine, master/slave rods are used rather than the simple type shown in the picture above. The master rod carries one or more ring pins to which are bolted the much smaller big ends of slave rods on other cylinders. Radial engines typically have a master rod for one cylinder and slave rods for all the other cylinders in the same bank. Certain designs of V engines use a master/slave rod for each pair of opposite cylinders. On the other hand, some V engines use simple rods side by side on a single crankpin, or separate crankpins for each cylinder. The radial engine is an internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel. ... A V engine is a common configuration for an internal combustion engine. ...

Steam engines

In a steam locomotive, the crank pins are often mounted directly on one or more pairs of driving wheels, and the axle of these wheels serves as the crankshaft. The connecting rods, also called the main rods, run between the crank pins and crossheads, where they connect to the piston rods. Crossheads are also used on large diesel engines manufactured for marine service. One of the last mainline steam locomotives built in the UK: British Railways Standard Class 9F 2-10-0 no. ... Piston and connecting rod from an automobile engine, showing the big end bearing at the bottom. ... On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotives pistons (or turbine, in the case of a steam turbine locomotive). ... A crosshead bearing (or simply crosshead) is used in large reciprocating engines, whether internal combustion engines or steam engines. ... In a piston engine, a piston rod joins a piston to a connecting rod. ...

The connecting rods of steam locomotives are usually of rectangular cross-section but, on small locomotives, marine-type rods of circular cross-section have occasionally been used. Stephen Lewin, who built both locomotive and marine engines, was a frequent user of round rods. Stephen Lewin of Poole, Dorset, England was a builder of steamboats and steam locomotives. ...

On Western rivers steamboats, the connecting rods are properly called pitmans, and are sometimes incorrectly referred to as pitman arms. A paddle steamer, paddleboat, or paddlewheeler is a ship or boat propelled by one or more paddle wheels driven by a steam engine. ... The Pitman arm is a steering component in an automobile or truck. ...

See also

• Steam locomotive components